Embodiments of the present invention relate to gas turbine engine fuel nozzles and, more particularly, to apparatus for supporting various structures within turbine engine fuel nozzles.
Aircraft gas turbine engines include a combustor in which fuel is burned to input heat to the engine cycle. Typical combustors incorporate one or more fuel injectors whose function is to introduce liquid fuel into an air flow stream so that it can atomize and burn.
Staged combustion systems have been developed to limit pollution, increase efficiency, lower cost, increase engine output, and improve operability. In a staged combustion system, the nozzles of the combustor are operable to selectively inject fuel through two or more discrete stages, each stage being defined by individual fuel flowpaths within the fuel nozzle. For example, the fuel nozzle may include a pilot stage that operates continuously, and a main stage that only operates at higher engine power levels. The fuel flowrate may also be variable within each of the stages.
A typical fuel nozzle is a complex assembly including a nozzle tip mounted to a stem connected to a stationary portion of the gas turbine engine. The nozzle tip typically includes numerous internally-supported components, defining intricate, small cross-section passages for the flow of air and fuel. Portions of the fuel nozzle are exposed to high-temperature airflows and radiant heating, while other portions are isolated from heating and exposed to a flow of relatively cool liquid fuel. Generally, the hot and cold portions should be isolated to avoid thermal stresses and heat-induced carbon deposits (i.e. “coking”) in the fuel-bearing passages.
Furthermore, the entire fuel nozzle is subject to significant vibration at various frequencies. The internal support structures of the fuel nozzle must be stiff enough to avoid fatigue failure and undesired harmonic behavior, but also have some compliance in order to avoid load transfer from one component to another within the fuel nozzle.
Accordingly, it may be beneficial to have a fuel nozzle with internal structures that are mechanically and thermodynamically isolated.